A segment of Vanderbilt Drive will be shut down for nearly two years as Collier County replaces two aging bridges.

The $5.4 million project started early this month and will close most of Vanderbilt Drive from 111th Avenue to Wiggins Pass Road until the early summer of 2018.

The two bridges, which cross a small tidal creek and Little Horse Pass, were built in the 1960s and will be replaced one at a time. Up first is the smaller bridge about a mile north of 111th Avenue. The work will take five months. Once completed the bridge will be open to local traffic while the road will be shut down a half mile to the north as crews replace the second bridge, which runs from the Anchorage Condominiums to the Marina Bay Club.

The new bridges will be built to last 70 years, said Connie Deane, county spokeswoman.

“This is the quickest way we could do it,” Deane said. “There’s no way we could have gotten vehicles or bicycles through while we’re working there. It’ll be a little bit of an inconvenience but it’s necessary in order to replace those bridges, which are beyond their useful life.”

Vanderbilt Drive runs through the winding mangroves and tidal creeks near Delnor Wiggins State Park. It has a small gravel shoulder used by kayakers and canoers to launch into the shallow estuaries that lead to Wiggins Pass and Barefoot Beach and connect north up to Estero Bay and beyond.

The two bridges, built in 1964, were deemed functionally obsolete by the state Department of Transportation during an inspection in 2012.

They are past their useful life, but are still structurally safe to cross.

The new bridges will be wider and the roadway approaching the passes will be repaved. A turn-lane will be added at the road’s intersection with the Marnia Bay Club.

The crossings will also be designed to fit a 10-foot-wide bike path that is being built from 111th Avenue to Bonita Beach Road. The bike path will replace a 6-foot-wide sidewalk, often crowded with joggers, beach goers and bicyclists, and is expected to be completed by spring of 2017.

Taxpayers will only have to pick up about half of the $2.3 million cost of the new path. Developers of five high-rises at the nearby Cocohatchee Bay PUD will cover $1.6 million of the tab as part of a 2008 deal with the county to settle a lawsuit over the size of the high-rises.

The county will be able to save and relocate a pedestrian bridge that crosses Little Horse Pass once the new path is built, Deane said.